Respect pre-defined DOCKER_IMAGE value in binary_populate_env.sh (#24787)
Summary:
`binary_populate_env.sh` is used by `binary_linux_test`, and for libtorch with new ABI we need to run the tests on a docker image different from `soumith/manylinux-cudaXX`. In such cases, we should respect the actual DOCKER_IMAGE value defined in the CircleCI job description.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24787
Differential Revision: D16867976
Pulled By: yf225
fbshipit-source-id: dc0a68bffc5789249ae14491ef485c7cc2fc1c34
